A computer system like a notebook has an embedded controller (EC) for controlling a power management of computer system, a battery charging operation, and a rotation rate of the fan. The power management includes the power control in operating in a power on status and a power off status.
Because the power management is controlled by the embedded controller, the embedded controller must be kept in an alive status in the computer. Therefore, even the computer jumps to a sleep status or a power off status, the embedded controller is still keeping in an alive status. Hence, the power of the embedded controller is provided by a standby power, the standby power is provided by a battery in the computer.
FIG. 1 is a diagram showing a power control circuit and method of an embedded controller in a traditional computer system. The battery voltage (Vbat) of the battery is provided to a regulator 10, and the regulator 10 sends an embedded controller voltage (VEC) to the embedded controller 20. The embedded controller voltage (VEC) is the standby power and it's about 3V.
The regulator 10 had an enable pin (EN). A first resistance (R1) connects the battery voltage (Vbat) and the enabled pin (EN). When the battery is installed into the computer, the enable pin (EN) is in the high level voltage and makes the regulator 10 operate, and the regulator 10 provides an embedded controller voltage (VEC) to the embedded controller 20. After the embedded controller 20 receives the embedded controller voltage (VEC), the embedded controller 20 will output a power on signal (PW_ON) in a high level voltage.
A traditional embedded controller 20 connects to a power button in the computer system for receiving a button signal. If the power button is not pressed, the button signal keeps in a high level voltage. On the contrary, when the user presses the power button, the button signal keeps in a low level voltage, and the period of the pressing time is the term that keeps in the low level voltage. When the embedded controller 20 detects that the button signal is in the low level voltage, the embedded controller 20 will send a plurality of power control signals to wake up the other device and operate in the computer.
However, when the battery is installed into the computer, the regulator 10 and the embedded controller 20 will continuously consume the energy of the battery. Generally, the quiescent current is about 3˜5 ma, if the battery is installed into the computer product for a long shelf time, the user may not power on the computer by the remaining energy of the battery after purchasing.